rtc: ds1307: fix kernel splat due to wakeup irq handling

Since commit 3fffd128 ("i2c: allow specifying
separate wakeup interrupt in device tree") we have
automatic wakeup irq support for i2c devices. That
commit missed the fact that rtc-1307 had its own
wakeup irq handling and ended up introducing a
kernel splat for at least Beagle x15 boards.

Fix that by reverting original commit _and_ passing
correct interrupt names on DTS so i2c-core can
choose correct IRQ as wakeup.

Now that we have automatic wakeirq support, we can
revert the original commit which did it manually.

Fixes the following warning:

[   10.346582] WARNING: CPU: 1 PID: 263 at linux/drivers/base/power/wakeirq.c:43 dev_pm_attach_wake_irq+0xbc/0xd4()
[   10.359244] rtc-ds1307 2-006f: wake irq already initialized

Cc: Tony Lindgren <tony@atomide.com>
Cc: Nishanth Menon <nm@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>